Method of preventing silverware



Patented May 21 1946 I v t I I 2,400,786v

NlTED STATES PATENT oFFicE I 13 ,400,; 7 t I Y No Drawing. Application April 7, 1944, a

.. Ser al No. 530,065

5 (cam-134) I This invention relates to a method of retardpolyethylene polyamines (ex-g}, diethylene triproblem which is annoying and labor-consummolecule.- Both saturated and unsaturated acids been suggested to protect silverware by confining spirit thereof.

- the silverware to a restricted space. bright appearance and remains bright even after ing the tarnishing of silver, withparticular refamine, triethylene tetramine; tetraethylene penerence to retarding the surface staining of silvertamine, etc.) For use in the present invention ware. guanidine and substituted guanidines are con-'- The ready tendency for surfaces of silver to 5 verted into their fatty acid salts.

tarnish andstain on exposure to ordinary atmos- As fatty acid I can use aliphatic carboxylic pheric conditions presents a constant cleaning acidspossessing ten or more carbon atoms in the ing. A solution of this problem would be of defiare satisfactory, suchas iauric, stearic, palmitic, nite benefit not only to stores having silverware lo oleic and the fatty acids of vegetable and animal on exhibit but also to households where such oils and fats. Considering cost and ease of use, silverware as candlesticks, bonbon dishes, trays, oleic acid is suitable.

etc., are usually left exposed on tables, side- The description given in the following examboards, etc., and consequently need frequent ples shou d t be construed as lim bu 5 cleaning. it by way of illustration since those skilled in the It has been suggested to protect silverware by art may make variations in the process of this applying a thin coating of collodion. It has also invention without departing from the scope and it in a restricted spaced exposed to the vapors of Example 1.-One mole of stearic acid is reacted a voltaile amine. While this might be accomwith /2 mole of guanidine carbonate. 'A 2% plished under certain conditions in a store, it aqueous solution of guanidine stearate is made would be impractical in a home. and applied to silverware by impregnating a cothave now found a practical solution for subton wad with the solution, rubbing this wad-- stantiaily retarding the formation of tarnish lightly Ov cl n verw re, a wing the film to films and stain on the surfaces of silverware dry and giving it then a slight bufiiing. After without any necessity whatsoever of confining application and buifing the silverware has a It is known that guanidine and substituted a month's exposure to ordinary atmospheric conguanidines may be neutralized byan aliphatic ditions. acid to give water-soluble products. I have now 80 Example z.0ne mole of coconut oil acids is found that water-soluble guanidine salts of alireacted with /2 mole of guanidine carbonate.- phatic acids exert an excellent protective action A 2% solution of the above reaction product is on silverware. then made in a mixture of of isopropanol In practising the invention it is merely necesand 68% of water. .The solution is applied to sary to coat the silverware with a dilute solution 85 silverware in the a e d ed in Ex p e 1.

of a water-soluble guanidine salt. A'satisfactory Silverware'so treated remains bright after one method of accomplishing the above is to make a month. I 1% to about 5% (preferably a 2%) solution, im- Example ate-One mole of oleic acid'is reacted pregnate with this solution a wad of cotton, then with mole of guanidine carbonate. A 2% sorub this wad lightly over clean silverware, maklution of the above reaction product is then made ing certain that a film is left'nn every part of in a mixture of 60 parts of isopropanol and 135 the surface. which is to be protected.,, The film is parts of water. The solution is applied to silverthen allowed to dry and given /slight'bufflng. ware in the manner described in Example 1. The solutioncan also be applied by dipping or Silverware so treated remains bright after one spraying. Silverware so treated will remain unmonth.

tarnished for. periods over a month when left in Example 4.-0ne mole of stearic acid is reacted ordinary atmospheric conditions while an unwith 1 mole of diethylene triamine-guanidine (a treated piece will be'badly stained and tarnished substituted guanidine made by heating equimowhen left under similar conditions. lecular proportions of guanidine carbonate and Substituted guanidines suitable for use herein diethylene triamine). A 2% solution of the remay be formed by heating a primary amine with action product is then'made and applied to sil- "guanidine (or guanidine carbonate), whereby verware in the described manner. Silverware reaction occurs with the evolution of ammonia. so treated remains bright after one month. As primary amines for this purpose I prefer to Example 5.Two moles of stearic acid are reuse compounds such as ethylene diamine and acted with 1 mole of diethylenetriamine-guanlequimolecular proportion of guanidine carbonate and diethylene triamine). A 2% solution'of the reaction product is then made and applied to Y silverware in the described manner. Silverware I tarnishing which comprises applying to the surface thereof a dilute aqueous solution of a fatty acid salt of a compound selected from the group consisting of guanie and substituted guanidine (a substituted guanidine made by heating dines, removing the water therefrom and bufling the surface, the fatty' acid of the salt containing more than 10 carbon atoms. 3. A process for protecting silverware from tarnishing which comprises depositing on the surface thereof a thin continuous film of guanidine stearate. v

4. A process for protecting silverware from tarnishing which comprises depositing on the surface thereof a thin continuous film of guanidine oleate. 

